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Slideback Voltmeter

IP.com Disclosure Number: IPCOM000092058D
Original Publication Date: 1968-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Evans, JE: AUTHOR

Abstract

A source of uncertainty in the measurement of small pulse amplitudes with slideback voltmeters is the voltage drop across the series diode. The circuit reduces this uncertainty. The following procedure to measure the amplitude of pulses from pulse generator 1 is used. Measure the output of pulse generator 1 into its rated load impedance R2 to determine approximate amplitude. With switch SW1 set to position A, adjust R1 so the DC voltage between points B and F is approximately equal to the voltage measured in first step. Set the oscilloscope to the most sensitive voltage scale or to 5 millivolts per centimeter whichever is greater. The scope must be set to display DC levels. Short-circuit the input of the scope and adjust the zero voltage level to a convenient reference point on the screen.

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Slideback Voltmeter

A source of uncertainty in the measurement of small pulse amplitudes with slideback voltmeters is the voltage drop across the series diode. The circuit reduces this uncertainty. The following procedure to measure the amplitude of pulses from pulse generator 1 is used. Measure the output of pulse generator 1 into its rated load impedance R2 to determine approximate amplitude. With switch SW1 set to position A, adjust R1 so the DC voltage between points B and F is approximately equal to the voltage measured in first step. Set the oscilloscope to the most sensitive voltage scale or to 5 millivolts per centimeter whichever is greater. The scope must be set to display DC levels. Short-circuit the input of the scope and adjust the zero voltage level to a convenient reference point on the screen.

With the system set up as described, move SW1 to position B and adjust R3 to display a DC level of 25 millivolts on the oscilloscope.

Move switch SW1 to position A and adjust R1 until the pulse amplitude being measured is at the 25 millivolt level displayed on the oscilloscope. Repeat the two previous steps until no adjustment of R1 and R2 is required. Disconnect pulse generator 1 and with switch SW1 in position A carefully measure the DC voltage between points D and F by a device having accuracy and resolution of 50 microvolts at any voltage less than 1.0 volts and whose input impedance is in excess of 10 meg ohms at balance or null.

The value thus measured...